P18-6 Sampling Rate Discrimination: 44.1 kHz vs. 88.2 kHz—Amandine Pras, Catherine Guastavino, McGill University - Montreal, Quebec, CanadaIt is currently common practice for sound engineers to record digital music using high-resolution formats, and then down sample the files to 44.1 kHz for commercial release. This study aims at investigating whether listeners can perceive differences between musical files recorded at 44.1 kHz and 88.2 kHz with the same analog chain and type of AD-converter. Sixteen expert listeners were asked to compare 3 versions (44.1 kHz, 88.2 kHz, and the 88.2 kHz version down-sampled to 44.1 kHz) of 5 musical excerpts in a blind ABX task. Overall, participants were able to discriminate between files recorded at 88.2 kHz and their 44.1 kHz down-sampled version. Furthermore, for the orchestral excerpt, they were able to discriminate between files recorded at 88.2 kHz and files recorded at 44.1 kHz. Convention Paper 8101

I also don't understand why a 192kHz DAC is supposedly cheaper to build. It is cheaper to build a good sounding 96kHz ADC than a 44.1kHz one, since the latter needs brickwall filtering. But oversampling DACs have quite relaxed filtering requirements already. So why should a 192kHz version be cheaper to build than a 44.1kHz version?

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Thank you, krabapple! The data itself shows not a proof but a 'tendency' that the summary is quite fishy... For anyone claiming that p=0.1 is a 'tendency' that could not be called a baseless offense, I guess.

Upsampling and oversampling differ, at least in terms of purpose and implementation.

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I also don't understand why a 192kHz DAC is supposedly cheaper to build. It is cheaper to build a good sounding 96kHz ADC than a 44.1kHz one, since the latter needs brickwall filtering.

Actually, they both need and get brickwall filtering. Some high sample rate DACs have a slow drop in response above 20 KHz, to like maybe 6 dB down at Nyquist. Then they have the usual sharp cutoff. From a digital filter desgn viewpoint it is all pretty much the same. The gentle roll off is window dressing. They still need a fairly complex digital filter to get the 90+ dB rejection above Nyquist. Some DACs are programmable to work either way. How moot does that make things?

Putting a gentle ramp a few feet high in front of the brick wall does not mean a signficiantly gentler stop when you hit the brick wall! ;-)

Chip speed and real estate is so cheap that people will put features like 192 KHz sample rate into the chip to help make sure it gets bought no matter what. A chip that does not work well at 44.1 is crap in any design engineers book because that is the bread and butter. If you make it run at 192 then maybe it iwill sell a few more < $200 surround receivers to ignorant Joe six-pack types who think that anything with bigger numbers is better.

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But oversampling DACs have quite relaxed filtering requirements already. So why should a 192kHz version be cheaper to build than a 44.1kHz version?

In fact what has happened is that 192/24 DAC chips have been under $1.00 in production quantities for years. I've found them in $50 DVD players. The circuit board space they sit on costs about as much as the chip if not more. You no longer pay a signficiant premium for > 44 KHz audio DACs. If you pay a premium, you pay it for improved dynamic range and low distortion. The premium you pay for magnificant performance is far less than it was even 5 years ago. There is stuff out there with 120 dB converters for less than $200.

Actually, they both need and get brickwall filtering. Some high sample rate DACs have a slow drop in response above 20 KHz, to like maybe 6 dB down at Nyquist. Then they have the usual sharp cutoff. From a digital filter desgn viewpoint it is all pretty much the same. The gentle roll off is window dressing. They still need a fairly complex digital filter to get the 90+ dB rejection above Nyquist. Some DACs are programmable to work either way. How moot does that make things?

Putting a gentle ramp a few feet high in front of the brick wall does not mean a signficiantly gentler stop when you hit the brick wall! ;-)

That's not the way it works. The reconstruction filter is necessarily analog. A 192khz DAC doesn't need 90dB of rejection at 20kHz. It only needs it at 96kHz! On a DAC with that sampling rate, the filter is very gentle. It may hit the -3dB point at 20-25kHz and gently roll down to -90dB at 96kHz. But the 44.1kHz sampling rate DAC needs to roll down from 20kHz to 22.05 khZ - that's steep!

Actually, they both need and get brickwall filtering. Some high sample rate DACs have a slow drop in response above 20 KHz, to like maybe 6 dB down at Nyquist. Then they have the usual sharp cutoff. From a digital filter desgn viewpoint it is all pretty much the same. The gentle roll off is window dressing. They still need a fairly complex digital filter to get the 90+ dB rejection above Nyquist. Some DACs are programmable to work either way. How moot does that make things?

Putting a gentle ramp a few feet high in front of the brick wall does not mean a signficiantly gentler stop when you hit the brick wall! ;-)

That's not the way it works.

You've denied quite a bit, surely its not *all* wrong.

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The reconstruction filter is necessarily analog.

Yes, but it is designed for the oversampling frequency. This puts it octaves above the nyquist frequency for the wave being converted.

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A 192khz DAC doesn't need 90dB of rejection at 20kHz. It only needs it at 96kHz!

I never meant to say that and on review, I didn't say that. I said "They still need a fairly complex digital filter to get the 90+ dB rejection above Nyquist." Note, I said nyquist, not 20 KHz. What I did say about 20 KHz is "Some high sample rate DACs have a slow drop in response above 20 KHz, to like maybe 6 dB down at Nyquist." Now what I said was a bit in error about the "6 dB down at Nyquist", what I really meant is "6 dB down just a bit below Nyquist".

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On a DAC with that sampling rate, the filter is very gentle. It may hit the -3dB point at 20-25kHz and gently roll down to -90dB at 96kHz.

It may do a lot of things (Like the Wolfson 8741) including exctly what I said.

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But the 44.1kHz sampling rate DAC needs to roll down from 20kHz to 22.05 khZ - that's steep!

Actually, a number of AKM audio DACs are only 6 dB at Nyquist (22.05 KHz for 44.1 SR) The steep part of the slope is above Nyquist.